1. Field of the Invention
Embodiments of the present invention relate to a technique for detecting faulty discharge at nozzles of an ink jet recording apparatus which performs recording by discharging ink droplets from the nozzles, and to an ink jet recording apparatus which may perform recording without using nozzles in a faulty discharge state.
2. Description of the Related Art
There are known ink jet recording apparatuses which use the ink jet method, as apparatuses for performing printing recording on recording media such as recording sheets and film and the like. An ink jet recording apparatus is capable of being mounted with a recoding head where there are arrayed nozzles for discharging ink droplets, in accordance with the resolution of the images to be recorded. Characters and images may be recorded in the recording medium by discharging ink droplets from the nozzles while the recording medium is being transported, and fixing the ink droplets on the recording medium.
In recent years, there has been proposed a full-line ink jet recording apparatus capable of high-speed recording. A full-line ink jet recording apparatus has a recording head with nozzles disposed over a width of a direction intersecting the recording medium conveyance direction of the recording medium (hereinafter referred to as “recording medium width”), or wider.
With an ink jet recording apparatus of which the width of the recording head is smaller than the recording medium width, ink droplets are discharged while scanning the recording head in the direction of the recording medium width, and the recording medium is conveyed in the recording medium conveyance direction by a predetermined amount each time one scan of the recording head in the recording medium width direction is completed.
There is no need to scan the recording head in the recording medium width direction with a full-line ink jet recording apparatus, so ink droplets may be discharged on the recording medium while continuously conveying the recording medium. As a result, with a full-line ink jet recording apparatus, recording may be performed at higher speeds as compared to an ink jet recording apparatus of which the recording head is smaller than the recording medium width.
The recording head of an ink jet recording apparatus has an ink storage unit for storing ink, and an ink channel communicating between the ink storage unit and the nozzles. The ink channel has provided thereto an energy generating unit which provides discharge energy to the ink, and ink droplets are discharged from the nozzles.
With a recording head having such a configuration, there are cases wherein the ink solidifies within the nozzles in the event of not using for long periods of time, and foreign objects entering the nozzles externally. Also, there are cases wherein bubbles are generated within the nozzles for one reason or another, with the nozzles being filled with bubbles.
In the event that solidified ink, external foreign matter, or generated bubbles plug up the nozzle, this may result in faulty discharge, such as no droplets being discharged from the nozzle or the ink droplets landing on the recording medium at a position other than that intended. Particularly, with full-line ink jet recording apparatuses, the recording head has a width greater than the recording medium width, so the number of nozzles is also great. Accordingly, nozzles with a faulty discharge state (herein after referred to as “faulty discharge nozzles”) more readily occur.
In the event of recording characters and images using faulty discharge nozzles, this may also lead to lower quality of the recorded image, so various methods have been proposed for detecting faulty discharge nozzles and alleviating effects on the image quality.
Japanese Patent Laid-Open No. 2006-205742 discloses a faulty discharge detecting method where a test pattern is recorded in a recording medium and faulty discharge nozzles are detected. A scanner unit which reads image data of the image recorded on the recording medium is provided to the ink jet recording apparatus, and faulty discharge nozzles are detected by comparing an image which should be recorded with the image read into the scanner unit, i.e., the actually recorded image.
With the ink jet recording apparatus disclosed in Japanese Patent Laid-Open No. 2006-205742, at the time of detecting a faulty discharge nozzle, a recovery operation is performed to recover from the plugging of the faulty discharge nozzle. Also, nozzles which do not have faulty discharge (called “normal nozzles”) perform substitute droplet discharge where these nozzles perform ink droplet discharge instead of the faulty discharge nozzle, thereby alleviating deterioration in quality of the recorded image.
With the faulty discharge detection method disclosed in Japanese Patent Laid-Open No. 2006-205742, the faulty discharge nozzle in the recording head may not be identified from the test pattern image unless the positional relation between the recording medium and the recording head may be determined. With the faulty discharge detection method disclosed in Japanese Patent Laid-Open No. 2006-205742, there has been the need to record the edge portion of the test pattern in the recording medium width direction of the recording medium, in order to comprehend the positional relation between the recording medium and recording head.
However, with a full-line ink jet recording apparatus, the recording head is greater than the recording medium width, so the edge of the test pattern in the recording medium width direction may not be recoded on the recording medium.
Particularly, in the event of performing so-called “borderless printing”, there is the need to detect faulty discharge of the nozzles recording the edge portion of the recording medium as well, so it is desirable to perform borderless printing when recording the test pattern as well. As a result, the position relation between the recording medium and the recording head may not be known, so faulty discharge nozzles may not be identified, and recovery operations of the faulty discharge nozzles and substitute droplet discharge at normal nozzles may not be suitably performed.
Now, the position relation between the recording medium and the recording head may be identified from the position of the recording medium and the position of the recording head as to the ink jet recording apparatus, but in this case, conveyance precision of the recording medium and assembly precision of the recording head is a prerequisite, which might lead to increased costs of the ink jet recording apparatus.